Fatal assertion (duplicate key error) when replicating insert on capped collection

Run with `python buildscripts/smoke.py repro.js` 'use strict';   load('jstests/libs/parallelTester.js');   function cappedWorkload() { var conn = new Mongo(); var db = conn.getDB('test');   while (true) { try { if (Random.randInt(100) === 0) { db.foo.drop(); } db.createCollection('foo', {capped: true, size: 4096});   db.foo.ensureIndex({value: 1}); for (var i = 0; i < 10; ++i) { db.foo.insert({_id: i, value: 0}); } } catch (e) { // ignore } } }   // start the replica set var rs = new ReplSetTest({nodes: 3, startPort: 27017}); rs.startSet(); rs.initiate(); rs.awaitSecondaryNodes();   // start the workload threads var threads = []; for (var i = 0; i < 20; i++) { var t = new ScopedThread(cappedWorkload);   threads.push(t); t.start(); }   threads.forEach(function(t) { t.join(); });